The invention relates generally to accumulation conveyors and, more particularly, to pneumatically actuated accumulation conveyors.
Accumulation conveyors normally include a pair of support rails placed a preselected distance apart. These support rails receive a plurality of transversely positioned product or conveying rollers. The conveying rollers support product being conveyed and when rotated, transport the same in a particular direction. Positioned below the conveying rollers is an endless drive member, such as a conveyor belt, which is driven by a drive motor. The accumulation conveyor system is normally divided into a plurality of zones. Each zone of the conveyor is equipped with a product sensor for detecting the presence or absence of product at a particular position along the conveyor. Each of these sensors is operationally connected to a contact assembly attached to one or both of side rails positioned below the top run of the endless drive member. Each contact assembly includes a pneumatically or mechanically driven vertically reciprocal contact member which may be operationally interconnected with contact assemblies positioned in other zones of the conveyor.
In accordance with a particular control scheme dictating the selective movement of product along the conveyor, one or more of the contact assemblies are actuated to move the contact member into frictional contact with the endless drive member. When a particular contact member is in such frictional engagement with the endless drive member, the conveying rollers adjacent the control assembly are engaged by the top surface of the top run of the endless drive member and begin to rotate. This rotation in turn results in the transportation of product supported by the selected conveying rollers.
When it is desired to accumulate product within a particular zone of the conveyor, a signal is sent to the contact assembly within that zone. Receipt of this signal causes the vertical retraction of the contact member and hence moves the same out of driving engagement with the endless drive member. This in turn results in the disengagement of the top surface of the endless drive member from contact with the conveying rollers and thus, such conveying rollers cease rotation.
One area in which existing accumulation conveyors often experience inefficiencies is with the vertically reciprocal contact assemblies. When the contact member is placed in engagement with the lower surface of the top run of the endless drive member, excessive "belt pull" is often encountered. That is, due to the engagement of the top surface of the contact member with the endless drive member, the drive member encounters frictional resistance in a direction opposite to the direction of motion. This frictional resistance, or belt pull reduces the rotational efficiency of the conveying rollers and may disrupt the movement of product along the conveyor. Moreover, this frictional resistance causes excessive wear on the endless drive member and thus reduces its economic life. Additionally, for any given conveyor speed, the drive motor must compensate for belt pull and therefore energy costs are increased.
When the contact member of the contact assembly is placed in engagement with the endless drive member, the contact member absorbs vertical forces. Due to the particular structural configuration of these contact members, such vertical forces impose moments upon certain areas of the contact member. Over time, these forces may cause the structural deformation of the contact member. This in turn increases the frequency and cost of maintenance. Also, structural deformation of the contact member precludes uniform contact of the endless drive member with the conveying rollers. Uneven contact between the drive member and the conveying rollers reduces the efficiency of the accumulation conveyor, and frequently results in one or more "dead rollers," i.e. a conveying roller which is not properly engaged by the drive member.
Many accumulation conveyors have the endless drive member positioned in proximity to one of the supporting side rails. Consequently, most existing contact assemblies are dedicated to accumulation conveyors having the endless drive member positioned near one side support rail or the other and can not be adapted to operate on the opposing side of the conveyor. Lack of adjustability of the contact assemblies to be used in conjunction with accumulation conveyors having the drive member on one side or the other increases manufacturing costs. Furthermore, existing contact assemblies are often composed of a variety of different components that are both difficult to manufacture, and expensive to replace.
Therefore, there exists a need for a contact assembly for an accumulation conveyor which overcomes the difficulties of the prior art while being exceptionally functional and economical to manufacture.